Title

Strip Sequencing and Speed Optimization of Continuous Cold Rolling Tandem Mills

Strip Sequencing and Speed Optimization of Continuous Cold Rolling Tandem Mills

Authorship

FINSTERLMANN, GERHARD; AFLENZER, HELMUTH; MITTER, FRANZ; WINKLER, ROMAN

FINSTERLMANN, GERHARD

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AFLENZER, HELMUTH

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MITTER, FRANZ

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WINKLER, ROMAN

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DOI

10.5151/2594-5297-LAC01867

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Abstract

Continuous operation and linked processes in cold rolling and strip processing are key elements in efficient, high-quality cold-strip production, and important technologies have been developed in this field over the past decade to equip a number of new and modernized plants with such capabilities. Some conventional continuous working procedures in strip processing lines have been established technologies for quite some time, however,processing, cold rolling and-to a certain degree-various surface-treatment and coating technologies all combined into one line are presently the subject of a considerable amount of development. Strong competition in the flat-product markets and the increasing demand for high-quality products under tight cost conditions make the huge cost-saving potential and the ability to consistently produce high quality very attractive for the steel industry. This is certainly one of the driving forces behind the decisions made by flat producers to increase implernentation of such efficient processes. Operational experience clearly shows that the conversion from de coupled to coupled operations can be a very curnbersorne process. The underlying operational philosophy differs substantially from the level of experience of entrepreneurs, even if they are well established flat producers with conventional equipment. Deciding factors for full savings potential and consistently high quality are line availability and line efficiency in which the former is mainly a question of a well-established maintenance practice. The latter however depends on production planning and process control parameters, which during the first years of operation might be beyond the full control of the operation personnel. Even well established linked operations exhibit some degree of inefficiency. Some of which, related to the tem speed factor, are in practice inevitable. Others are mostly operator dependent and can be balanced with countermeasures by means of sophisticated control strategies. Tools to reduce linked line inefficiency are fairly new in the industry and are certainly one of the most encouraging fields for further improvernents. VAI as well known builder of turnkey plants and process technology for linked lines started very early extensive developments in this field and is able to offer a complete package of software and control tools, enabling linked lines to run at an utmost level of efficiency. This paper outlines the key elements of this performance package as the optirnized production scheduling for linked processes and the level 2 autornation tool "Link Master", which controls the entire production process of a linked line under premises like maximum throughput and a minimum of process speed variations. Examples frorn simulation and practical applications show the huge performance potentials; hence cost saving and product quality potential offered by these tools.

Continuous operation and linked processes in cold rolling and strip processing are key elements in efficient, high-quality cold-strip production, and important technologies have been developed in this field over the past decade to equip a number of new and modernized plants with such capabilities. Some conventional continuous working procedures in strip processing lines have been established technologies for quite some time, however,processing, cold rolling and-to a certain degree-various surface-treatment and coating technologies all combined into one line are presently the subject of a considerable amount of development. Strong competition in the flat-product markets and the increasing demand for high-quality products under tight cost conditions make the huge cost-saving potential and the ability to consistently produce high quality very attractive for the steel industry. This is certainly one of the driving forces behind the decisions made by flat producers to increase implernentation of such efficient processes. Operational experience clearly shows that the conversion from de coupled to coupled operations can be a very curnbersorne process. The underlying operational philosophy differs substantially from the level of experience of entrepreneurs, even if they are well established flat producers with conventional equipment. Deciding factors for full savings potential and consistently high quality are line availability and line efficiency in which the former is mainly a question of a well-established maintenance practice. The latter however depends on production planning and process control parameters, which during the first years of operation might be beyond the full control of the operation personnel. Even well established linked operations exhibit some degree of inefficiency. Some of which, related to the tem speed factor, are in practice inevitable. Others are mostly operator dependent and can be balanced with countermeasures by means of sophisticated control strategies. Tools to reduce linked line inefficiency are fairly new in the industry and are certainly one of the most encouraging fields for further improvernents. VAI as well known builder of turnkey plants and process technology for linked lines started very early extensive developments in this field and is able to offer a complete package of software and control tools, enabling linked lines to run at an utmost level of efficiency. This paper outlines the key elements of this performance package as the optirnized production scheduling for linked processes and the level 2 autornation tool "Link Master", which controls the entire production process of a linked line under premises like maximum throughput and a minimum of process speed variations. Examples frorn simulation and practical applications show the huge performance potentials; hence cost saving and product quality potential offered by these tools.

Keywords

Throughput optirnization, criteria for strip sequence, accumulator and bottle neck analysis, optimization by means of "TabuSearchn, rolling speed optimization for all line sections, influente on strip quality performance, sequential quadratic programming.

Throughput optirnization, criteria for strip sequence, accumulator and bottle neck analysis, optimization by means of "TabuSearchn, rolling speed optimization for all line sections, influente on strip quality performance, sequential quadratic programming.